What does 'only good' mean? Say a sporting story, someone is very good, works very hard, but in the end loses in their last chance at a contest, and we say 'What a tragedy'. But, someone had to win, so others had to lose, that's how we set up contests. Could a perfectly good God make it so everyone wins? And winning still mean anything..? This is in the realm of Omnipotence Paradoxes.
Evil is a problematic word, because it carries so much baggage it lends itself to talking at cross-purposes unless a discussion-specific definition has been agreed. Kant had the idea of Radical Evil, something like being controlled by a temporary local concern that separates someone from following universal laws which best support overall wellbeing. But even he is criticised for shifting his terms over time, because he saw evil as both an innate inclination, and as something we are judgeable for having done. There are so many ways to define evil, have a look at the list here: Does philosophy have a dark side?
Nietzsche understood tragedy as part of the antidote to nihilism, the loss of personal meaning and social cohesion from an old meaning-cosmology or metanarrative no longer working but a new one not yet having arrived, or as foundational to a dynamic meaning-cosmology.
"Around the hero everything becomes a tragedy; around the demigod
everything becomes a satyr-play; and around God everything becomes —
what? perhaps a 'world'?" -in The Birth of Tragedy
It is said that only in economically prosperous times of peace, do the most unhappy and tragic stories get made into films, and vice versa in troubled times people seek escapism. Aristotle in his Poetics used the previously medical term for purging poisons 'catharsis', to apply to experiencing vicarious negative emotions in watching a tragedy, and feeling some release from or making peace with those. It is a poor consolation to someone tragically bereaved to say you will find a way to make sense of what happened, and yet to live their best life the bereaved must in fact do that. Tragic stories can help us practice, for the sorrows and disappointments we must face, must risk, in order to live fully.
It is widely noted Hollywood doesn't make films with unhappy endings. The area I think this is of most concern is in remembering war, because it means holding on to the idea there will be some kind of just results, that the 'true patriot' will come out ok. But war isn't like that, it's a Pandora's Box, that whatever good we find at the bottom opening releases unknowable unpredictable unjust evils. It is deeply unwise to only remember it's heroes, and not that above all war is tragic.
"The wheel of Fortune turns; I sink, debased;
another is raised up; lifted too high,
a king sits in his turn, him beware of ruin!
Beneath the axle we read: Queen Hecuba."
-from the medieval poem Fortune
Plango Vulnera, which was set to music by Carl Orff in his Carmina
Hecuba was queen of Troy, who had 19 children all of whom she saw die before her, and saw the city she had been queen of annihilated.
The trade-offs that not everyone can get what they want, and unforeseen unwanted consequences of getting or doing what we want, mean the possibility of tragedy is then part of living a meaningful life - taking risks for rewards, and understanding what it is to choose wisely.
In Buddhist thought, suffering arises from the chain of dependent origination, which begins with ignorance, forgetting the true nature of things and so grasping for what cannot be held. In the rebirth picture, there will always be justice and balance in time, and tragedy would be an experience we can use to help return to a proper understanding, ie of the three marks of existence. I mention this because it's a picture where all evil and tragedy can be redeemed, by using them as pointers back towards our original state of Bliss, in Awakening. So, through reframing the circle can be squared, in some sense.